The invention relates to a cooling system for a package in which electronic circuit components are mounted on a wiring substrate.
A prior art cooling system of this type is disclosed in a paper entitled "A Conduction-Cooled Module for High-Performance LSI Devices" by S. Oktay and H. C. Kammerer, published in the IBM J. RES. DEVELOP. Vol. 26, No. 1, pp. 55-66, January, 1982. The module disclosed in FIG. 1 in the paper comprises a multi-layer ceramic substrate, semiconductor chips mounted on the substrate, a hat covering the substrate, cavities formed in the hat, pistons resting in the cavities, springs pressing the pistons against the chips, helium gas filling a space defined by the substrate and the hat, a cold plate through which water flows, and an interposer inserted between the cold plate and the hat. In the module, heat generated from the chips is conducted to the cold plate through the pistons, the helium gas, the hat and the interposer. The module has a thermal-conduction coefficient of no more than 0.1 to 0.5 W/cm.sup.2 .degree. C. because of a small effective area for thermal conduction. As a result, the module has a disadvantage in that its cooling capacity becomes insufficient to cool integrated circuit chips as the chips come to consume more power with increasing circuit densities in the chips.
Another prior art cooling system is disclosed in U.S. Pat. No. 5,050,037. The system comprises a printed circuit board assembly having a printed circuit board 22, heat generative electronic circuit components 26 mounted on both faces of the board 22, and a pair of liquid-cooling modules 30a and 30b arranged on both sides of the board 22. Each of the modules 30a and 30b is provided with a liquid-cooling plate 32 having coolant supply heads 36 and resilient heat transfer units 40 held by the plate 32 and arranged in compressive contact with the components 26 on both faces of the board 22. Each of the heat transfer units 40 has a hollow resilient member 42 constructed as a bellows which must have an appropriate resiliency sufficient to ensure a stable contact between the unit 40 and the component 26 while absorbing any slight differences in the heights of the components 26. To gain a sufficient resiliency, the resilient member 42 is required to be formed thinly, resulting in a disadvantage in that liquid coolant flowing through the heat transfer unit 40 may leak out since the resilient member 42 is apt to easily develop a hole caused by erosion because of its thinness.